Control means for positive displacement rotary pumps and hydraulic motors



p 23, 1953 E. E. WAGNER 2,853,0221.

' CONTROL MEANS FOR POSITIVE DISPLACEMENT ROTARY PUMPS AND HYDRAULICMOTORS Filed June 17, 1955 2 Sheets-Sheet 2:

IN VEN TOR.

United States Patent() CONTROL MEANS FOR POSITIVE DISPLACEMENT ROTARYPUMPS AND HYDRAULIC MOTORS Ernest E. Wagner, Santa Ana, Calif.

Application June 17, 1955, Serial No. 516,167

8 Claims. (Cl. 103-120) This invention relates to a control means forpositive displacement rotary pumps and hydraulic motors of the variablevolume type.

In pumps and hydraulic motors of the type referred to, all looseness,deflection and sponginess, collectively designated as backlash,interferes with the smooth and efficient operation and hence isdetrimental to the pumps and hydraulic motors and to their performance;and therefore an essential object of the invention is to provide a meansby which backlash is eliminated for the life of the unit.

In conventional units of this type the resistance to movement of thestroke adjusting means is objectionable and therefore, an additionalobject of this invention is to provide a stroke adjusting mechanism inwhich resistance to movement under load is reduced to a minimum.

A further object of the invention is to provide a device of thecharacter referred to, which is of great simplicity, ease of manufactureand assembly.

Since the traverse of the inlet-outlet passageways from the intake sideto the outlet side of a unit of the character referred to results in animbalance of the control means along the line of its movement, it is afurther and important object of the invention to provide means foreliminating the effects of this imbalance, or so reduce them as to benegligible and more closely offset than is possible with conventionalmeans.

It is a further object of this invention to provide control meanswherein surfaces which must slide are not subjected to loads due to theoperating pressure when moving, and wherein surfaces which arenecessarily subjected to loads due to the operating pressure whenmoving, do not slide, but roll.

Other objects and advantages will become apparent from the followingdescription in connection with the accompanying drawings, in which,

Fig. 1 is an enlarged transverse sectional view taken on line 1-1 ofFig. 5.

Fig. 2 is a view of a unit looking at the inlet-outlet end.

Fig. 3 is an enlarged fragmentary sectional view through a set of rackand gear teeth. t

Fig. 4 is an enlarged longitudinal vertical section through a unit online 4-4 of Fig. 2.

Fig. 5 is a view of the left side, facing the shaft end.

In rotary pumps and hydraulic motors which displace fluid by radialaction, due to excentricity between rotor and housing, there arealternating forces of considerable magnitude along the line F-F of Fig.1, which line must pass through the center of rotation B of the rotorand the center A of the ring 13. The distance A-B or AL-B is variable,equal to the pump excentricity and proportional to the stroke of thecontrol means, which is a stroke adjustor as hereinafter pointed out.The pump excentricity is responsible for the pumping action.

The load on the unit, caused by the operating pressure, oscillates asthe pumpingchambers are alternately loaded and unloaded upon enteringand leaving the pressure 2,853,022 Patented Sept. 23, 1958 ice side of apump or hydraulic motor of the radial displacement type. One componentof the load, by far the greatest proportion, is transferred to the pumphousing through a stroke adjustor and the other component is transferredat right angles along the line F-F to a stroke actuating mechanismpresently referred to. This latter component represents the alternatingforce or forces responsible for the imbalance.

The forces are large, diametrically opposed and therefore capable ofsetting up a violent, disturbing and destructive pounding action. Toprevent this, no looseness can be tolerated and all parts of the strokeadjusting mechanism should be preloaded at all times, the preload toexceed the magnitude of the reciprocating forces.

Referring more particularly to the drawings, my invention comprises acircular, rollable stroke adjustor 10 with antifriction elements 11 and12 supporting the ring 13 of a cartridge type pump or hydraulic motor,the rotor assembly 14 of which is carried in antif'riction bearings15-16 in a suitable housing 17.

For such other adjuncts as may be employed to form the composite unitshown in Fig. 4, but which form no part of the present disclosure,reference is made to my co-pending applications Ser. No. 468,815, filedNovember 15, 1954 covering Rotary Device and Ser. No. 490,605 filedFebruary 25, 1955 covering Plate Valve for Rotary Units.

Therollable stroke adjustor 10 has an exterior cylindrical surface 23,which surface coincides with the pitch line of a gear with standardinvolute teeth, said teeth having been modified by decapitating theirtops 24 at the pitch line to form a partial gear composed of not lessthan two of said modified teeth, diametrically opposed. Racks 26-27 haveteeth 30-31 which have been correspondingly modified by leaving thenormal profile 25 solid below their pitch lines 28-29 in order to formsurfaces 38-39 upon which the decapitated teeth may truly roll, so thatthe center of the stroke adjustor 10, upon rolling, will generate astraight line that is common to both the center of the rotor and saidcenter of the stroke adjustor, for which reason the pitch lines 28-29 ofthe racks 26-27 must be parallel to said straight line.

The rack teeth 30-31, Fig. 3, adjacent to the stroke adjustor tooth 34engage the gear tooth spaces 32-33 in such a manner that the points ofcontact 36-37 between the mating tooth fianks touch first, before theload causes the tooth 34 to contact its mating surface at the point 38.

A preload is thereby established between the rack and the gear teethwhich effectively eliminates all lateral play by means of the loadimposed on the stroke adjustor by the fluid pressure of the pump,without impairing the freedom of the stroke adjustor to roll and therebyvary the distance between the center of the rotor and the center of thestroke adjustor for the purpose of varying the displacement of thepumping cartridge.

A further and important function of the preload is to reduce minutelateral movements due to elastic deformations under load changes.

For conditions of clockwise rotation, per arrow, the unit operating as apump with the stroke adjustor so positioned that the center ofexcentricity A is to the right of B, the vane pockets 22, see Fig. 1,below the line F-F, are decreasing in size and therefore generatingpressure, the result of which is principally a downward pressure on thestroke adjustor 10 and its tooth 34. The load on the tooth istransferred to the rack and through it to the stationary cover plate 93and the housing 17. Friction between rack and cover plate, due to theload, effectively locks the two against movement when' such movement isnot a normal operating function.

Upon moving the stroke adjustor to the left, Fig. 1, the center, pointA, passes through B to the position AL, to the left of B, which, as hasbeen shown in the references mentioned results in a flow reversal whenoperating as a pump, or a reversal in the direction of rotation whenassembled for operation as a hydraulic motor.

To simplify matters the description following pertains to a unitfunctioning as a pump. It is obvious, that the principle underlying theoperation as a pump applies equally to a unit operating as a hydraulicmotor, except for certain self-evident differences.

'I have shown that when the stroke adjustor center A is positioned tothe right of B there results a downward pressure on the stroke adjustorfor clockwise rotation.

With the stroke adjustor center A positioned to the left of B thepockets 40, above the line FF, are decreasing in size and are thereforegenerating pressure, the result of which is principally an upwardpressure on the stroke adjustor 10, its tooth 35, the rack 27 and thecover plate 88, therefore movement of the rack is effectively preventedby friction with the cover plate in a like manner to that for thedownward load.

This alternately loads rack 26 for discharge from pockets 22 and rack 27for discharge from ockets The design is therefore arranged to index rack26 against stop 41, where it remains when under load, while the rack 27,guided by the rack teeth and the surface 90 on the cover 88, but underno direct load from the downward pumping pressure, regulates the strokefrom B to A. The design is likewise arranged for rack 27 to indexagainst stop 42, where it remains when under load, while the rack 26,guided by the rack teeth and surface 89 on the cover 93, but under nodirect load from the upward pumping pressure, regulates the setting ofthe stroke adjustor for all positions between points B and AL. It mustbe understood that whenever the stroke adjustor moves from a positionconcentric to the rotor center B, even if only .001", one or the otherof the racks is always under load and, that, whichever rack is soloaded, that rack is also effectively held against movement by frictionwith its coverplate. The stroke adjustor 10 is held in alignment axiallyby the housing surfaces 91-92, Fig. 4. With the foregoing requirementsand actions in mind, the stroke actuating means functions as follows:

Light springs 43-44 bearing against plates 4546 on the racks 2627 keepthem in contact with the stops 41-42 whenever the plungers 47-48, withinthe cylinders 83-84, which are bolted to the housing 17, Fig. 2, arede-energized, that is, whenever the inlet-outlet connections 49-50 tothe plunger-s are connected to the atmosphere.

Two types of stroke adjusting means are shown in Fig. 1.

v The first type is shown in the upper right hand corner wherein thecover plate 51 contains a screw 52, axially adjustable in the threadedportion 55 of the cover plate 51. An internal spline 53 in the screw 52is slidably engaged by a mating spline on the end of the strokeadjusting shaft 54 which is journaled in bearing 56. O-ring 57 in anenlarged portion of the shaft prevents oil from escaping. The outer endof the stroke adjusting shaft 54 is arranged to receive a gear 58, asshown, but other actuating means better suited to the conditionsencountered may be substituted. The bearing 56 prevents shaft 54 frommoving axially. Actuating the gear 58 causes the screw 52 to move in orout as the mating splines 53 slide axially thereby adjusting theposition of the stop surface 59 with respect to the neutral position, inwhich position the rack 27 is against stop 42. The distance the rack isfree to move between the stop surfaces 42 and 59 is therefore a measureof the setting of the stroke adjustor center A, which setting isproportional to the rate of discharge of the pump.

The second type is shown in the lower left hand corner wherein the coverplate 60 blanks off a stroke adjusting means functioning as follows: Thescrew 61 operates in a manner identical to that of the screw 52. Thestop surface 62 is positioned by the stroke adjusting shaft 63, whichhas an O ring 66, and is journaled in bearing 64 in the cover plate 65.It is provided with a splined inner end 82 and is made identical to thestroke adjusting shaft 54, except for its extension 85 through a hole64a in the rack 26 in order to bring both stroke controls to the sameside of the unit. Screw 61 is carried in mating threads in adifferential piston 67 which is provided with an 0 ring 68 on its largediameter. The annular space 69 has an inlet-outlet connection at 70. Oring 71 is a static seal and O ring 72 a seal between the flanged cover73 and the movable differential piston 67. A stop ring 74 accuratelylocates the position of the differential piston axially, when fluidpressure is applied to the. annular space 69, therefore, actuating shaft63 positions screw 61 and its stop surface 62 to the position giving thedesired discharge rate. For any position of the stop surface 62,corresponding to a position of the stroke adjustor 10 short of themaximum stroke, and assuming plunger 47 to be energized, then, releaseof fluid pressure from the annular space 69 lets the differential piston67 move back, carrying the screw and the stop surface 62 with it, whichaction frees the stroke adjustor 10 to move to its maximum positionagainst stop 81, corresponding to a maximum rate of flow, without in anyway disturbing the setting for the lower rate. Upon re-establishingfluid pressure on the differential piston 67 the pump again operates atthe lower originally selected rate.

For machine tool applications this arrangement results in a selectivefeed rate over a wide range, coupled with a constant speed rapidtransverse by means of an on-off control.

The four bores 7576-7778 are identical in diameter and permit assemblyor reassembly, for right or left hand rotation, using the same parts.Cover plate 65 with shaft 63 can be substituted for cover plate 79, sothat rack 27 is adjustable from either side. Likewise, cover plate 60may be removed and another one, including a stroke adjusting shaft 54,substituted.

The plungers 47-48 are so proportioned that, in combination with thehydraulic pressure behind them, they exert a force against the strokeadjustor 10 which is always greater than the alternating force againstit.

With plunger 47 de-energized and plunger 48 energized by a suitablesupply of hydraulic pressure fluid, the center A of the stroke adjustor10 will move from the neutral position to the right and the strokeadjustor itself will roll with a clockwise motion because rack 26, underthe action of spring 44, is against the stop 41, while rack 27 is freeto move away from its stop 42, being held there only lightly by thespring 43. Movement of the stroke adjustor will continue until movementof the rack is arrested by the stop surface 59 on the end of screw 52.

Fig. 1 shows the screw set for maximum stroke. Should a screw settingexceed the maximum permissible, the stroke adjustor is then arrested inits movement by a safety stop, either or 81, as the case demands.

Upon de-energizing plunger 48 the stroke adjustor returns to the neutralposition under the action of spring 43 or returns at an accelerated rateif plunger 47 is energized. In so doing the stroke adjustor rolls withan anti-clockwise movement on rack 26 until the rack 27 is arrested inits neutral position by stop 42. Rack 26 is prevented from moving byreason of the friction between it and its cover plate, due to thepressure generated by the hydraulic fluid, whenever and as long as thestroke adjustors position is excentric to the rotor. Plunger 47continues to move the center of the stroke adjustor, therefore, withrack 27 arrested, rack 26 moves against the light force of spring 44 andcauses the stroke adjustor to roll with a clockwise movement on rack 27,transporting its center to the left, until stopped by the surface 62 onthe end of the screw 61.

We have already described the action and function of the diflerentialpiston 67, the proportions of which must be such, that the force itexerts, in conjunction with the hydraulic pressure, is great enough toreturn it to its initial position as dictated by the stop 74, whileovercoming the reciprocating force along the center line heretoforereferred to and moving the stroke adjustor against the opposing force ofthe plunger 47.

Seepage is drained from the unit via pipe connections 86-87 and covers88 and 93 when bolted in place complete the enclosure of the unit, seeFig. 2.

I claim as my invention:

1. In combination with a rotary unit including a rotor, radial membersmovably disposed in said rotor and a ring surrounding said members andforming pumping chambers developing a pressure differential, therebygenerating a radial force on said ring: a housing having covers, acircular stroke adjustor in said housing and held in axial alinementtherein by surfaces in said housing, the exterior surface of saidcircular stroke adjustor at diametrically opposite points having a geartooth decapitated at its pitch line, racks disposed within said housingand slidable on said covers, said racks having teeth adapted to meshwith the teeth on said stroke adjustor and providing surfaces betweensaid teeth upon which the tops of said decapitated teeth of saidcircular stroke adjustor may truly roll, while said radial force holdsstationary the companion rack associated with said adjustor, fixed stopsin said housing for each of said racks, springs to hold said racksagainst said stops while one or the other rack is free to move away fromits stop and means to roll said member to vary the eccentricity of saidrotary unit.

2. Means to control the volume and the direction of fluid flow in arotary hydraulic unit which includes a rotor, radial members movablydisposed in said rotor and a ring surrounding and cooperating with saidmembers to form pumping chambers generating a radial force on said ring:said means comprising a circular stroke adjustor surrounding said ringand having a gear tooth at diametrically opposite sides, a housing,racks slidably disposed within said housing and in mesh with said teethand movable in opposite directions, means for limiting the movement ofsaid racks and thereby controlling the magnitude of the stroke and thevolume of fluid flow, the radial force of said pumping chambers holdingone of said racks stationary whereas the other rack is free to move, andmeans to actuate said stroke adjustor in opposite directions and forcesaid adjustor to roll one way or another, thereby to control thedirection of fluid flow.

3. In combination with a rotary unit including a rotor, radial membersmovably disposed in said rotor and a ring surrounding said members toform pumping chambers: a housing, a stroke adjustor in said housingsurrounding said ring, two modified gear teeth upon the circumference ofsaid stroke adjustor and concentric with said ring, racks in saidhousing on diametrically opposite sides of said stroke adjustor and inengagement with said teeth, said stroke adjustor adapted to roll withone of said teeth upon one of said racks to vary the eccentricitybetween rotor and stroke adjustor in one direction and to roll with theother of said teeth upon the other of said racks to vary theeccentricity between rotor and stroke adjustor in the oppositedirection; said stroke adjustor, when displaced by rolling, being guidedby said racks in a straight line, parallel to a line common to thecenters of said stroke adjustor and rotor, means to selectively controlsaid eccentricity, and means to roll and automatically clamp said strokeadjustor in the position of eccentricity selected,

4. In combination with a rotary unit including a rotor, radial membersmovably disposed in said rotor and a ring surrounding said members: ahousing, a stroke adjustor surrounding said ring, said stroke adjustorhaving two teeth, one diametrically opposite the other, two racks withinsaid housing, said stroke adjustor engaging and being rollable upon oneor the other of said racks for varying the eccentricity of said ringwith respect to said rotor, means engaging said stroke adjustorsubstantially midway between said teeth for rolling said adjustor oneway for varying the flow in one direction, and means diametricallyopposite for rolling said adjustor the opposite way for varying the flowin another direction and means adapted to co-operate with said racks tocontrol the eccentricity of said ring.

5. In combination with a rotary unit including a rotor, radial membersmovably disposed in said rotor and a ring surrounding said members toform pumping chambers developing a pressure differential and thereby generating an outwardly directed radial force on said ring; a housing, astroke adjustor surrounding said ring, said stroke adjustor having asingle gear tooth substantially in line with said radial force and asecond gear tooth diametrically opposite, a slidable rack meshing witheach or said gear teeth for adjusting the stroke, adjustable stopscooperating with said racks, fixed neutral stops, springs indexing saidracks against said fixed stops, said radial force holding stationary therack co-acting with said force whereas the opposite rack remains free tomove, means for moving said stroke adjustor thereby to roll it on saidrack held stationary and slide said free rack until arrested by one ofsaid adjustable stops, said means also clamping said stroke adjustor tosaid housing.

6. In combination with a rotary unit including a rotor, radial membersmovably disposed in said rotor, a ring surrounding said members andforming pumping chambers: a housing, a circular stroke adjustor havingtwo decapitated gear teeth, one diametrically opposite the other on thecircumference thereof, racks in said housing, anti-friction meansbetween said ring and said stroke adjustor, said gear teeth meshing,free of backlash, with said racks, the tops of said teeth adapted toroll on the bottom of the spaces between the teeth of said racks, meansfor rolling said stroke adjustor, and means in said housing co-operatingwith said racks, selectively limiting the travel of said strokeadjustor.

7. A rotary unit including a housing having safety stops, a rotortherein having radial vanes and a ring surrounding said vanes anddisplaceable to vary the displacement of said rotor, a cylindricalstroke adjustor surrounding said ring and having two gear teeth, onediametrically opposite the other, racks meshing with the teeth on saidstroke adjustor to make it roll, diametrically opposed plungers of equalarea in said housing bearing against said stroke adjustor midway betweenthe pitch lines of said teeth, said plungers adapted to be actuatedalternately, one rolling said stroke adjustor in one direction, first onone rack and as zero stroke is passed, on the other rack, the other ofsaid plungers rolling said stroke adjustor in the opposite direction,first on one rack and upon passing zero stroke, upon the other rack,adjustable stops for limiting the travel of said racks, shafts foroperating said stops, a piston carrying one of said stops, said pistonbeing adapted to be held extended and to move back with said stop whenfluid pressure is released, thereby permitting said stroke adjustor tomove to its maximum position against one of said safety stops under theforce of one of said plungers.

8. Means to control the volume and direction of fluid flow in a rotaryhydraulic unit which includes a rotor, radial members movably disposedin said rotor, and a ring surrounding said members to form. pumpingchambers developing a pressure differential and thereby generating aradial force on said ring; a circular stroke adjustor having two teeth,a housing, a pair of racks slidable in said housing and each engagingone of said teeth on diametrically opposite sides of said strokeadjustor, one of said racks being held stationary by the radial forcegenerated by said pumping chambers, the other of said racks remainingfree to move and permit the stroke adj'usftoi f0 r611 6'11 saidstaticnafy rack, and inans to' aict'fiat e sai dtrok ddjustbi inopposite dir'etions to regulate the fiowih one of another dire'ction.

References Cited in the file of this patent 5 UNITED STATES PATENTS IAntonelli -1 Sept. 17, 1929 Rayburn Ian. 16, 1934 Ott Jan. 15, 1935 10Clark 1 July 18, 1939 Whitmo're Nov. 14, 1944 Dillon Aug. 26, 1947French June 17, 1952 Erns't Sept. 30, 1952 Garner Oct. 27, 1953 FOREIGNPATENTS Great Britain Aug. 22, 1956 France Jan. 10, 1951

